The recent advances in multimedia technology demand protection of digital images from unintentional manipulation for content integrity, copyright, and ownership. Digital watermarking technique has wide acceptance in the industry for anti-piracy, ownership verification, and digital image authentication. There have been a large number of schemes in the literature proposed for digital watermarking using non-cryptographic and cryptographic primitives. Use of Least Significant Bits (LSB) is one of the oldest but classical approaches for digital image authentication. Although LSB approach is efficient, it does not provide adequate security. Cryptographic primitives such as hash function, digital signature, and message authentication codes have been used in several applications including multimedia for data authentication. Digital signature-based image authentication provides strong security, but the approach requires managing public key infrastructure, which is a costly operation. Partial data protection is also an optimal approach for protecting important data while leaving unimportant data unprotected. Considering security weakness of the LSB-based approach and cost overhead of the public key-based approach, the authors present in this chapter a digital image authentication scheme using LSB, keyed hash, and partial encryption. They show that the proposed watermarking scheme is secure and efficient in comparison to other related schemes.
TopIntroduction
Recent advances in computing and communication technology allow easy access of digital content through the Internet (Furht, & Kirovski, 2004). The proliferation of Internet technology and accessibility of digital documents across the globe enable increasing copyright fraud, duplication of data and unauthorized distribution of multimedia content. Naturally, controls over copyright, anti-piracy and unauthorized content redistribution are potential challenges in digital economy, which needs significant attention from scientific community. One can use multimedia content from available source, but should take appropriate permission of the content owner and after giving due citation and credits to content owner. Fabrication of multimedia content, in particular manipulation of digital image, is certainly not allowed in any form irrespective of deliberate or (un)intentional attempt. When a dishonest person is getting away by doing such malpractices without being caught then it raises two important concerns - on one hand, the dishonest person knows that s/he can enjoy her/his life in this way without expecting any punishments; and on the other hand, it is because of poor content protection and detection mechanism by the content owner. Finally, it effects on the financial part at the owner side. Therefore, ensuring digital image integrity and image authenticity has become a major concern in multimedia security.
Cryptographic primitives such as encryption and digital signature have been used for data confidentiality and authentication, respectively. However, in multimedia data protection direct use of encryption and digital signature may not be of much help, as the data size is too large and most of the cases data hiding is important than simple encryption. Therefore, these primitives along with other primitives (e.g. hash function, chaotic map, pseudo-noise, etc) must be used for multimedia data protection as per application requirement. In order to protect multimedia data, techniques like digital watermarking, scrambling, authentication, integrity or a combination of these could protect digital content from content tampering. Many techniques (Walton, 1995), (Tang, Hwang, & Yang, 2002), (Hwang, Chang, & Hwang, 1999), (Yeung, & Mintzer, 1997), (Wong, & Memon, 2001), (Chang, Hu, & Lu, 2006), (Ahmed, Siyal, & Abbas, 2010) have been proposed for protecting multimedia data, piracy detection, and copyright and ownership control. Out of several approaches, digital watermarking (Furht, & Kirovski, 2004) technique has been playing a pivotal role in multimedia data protection.
Digital watermarking (Furht, & Kirovski, 2004) is a technique that inserts a piece of information into a target image, which can be later extracted for a variety of purposes and/or detected in case of malpractices. A watermark can be a binary string, a logo, or some intended features of the multimedia content. Whatever maybe the watermark content, the watermarking technique needs to be designed in such a way that unauthorized entity should not be able to identify any information about the watermarked content and position of it. At the same time, the content owner or authorized entity should be able to identify the watermarked information from the image as and when needed. Digital watermark can use non-cryptographic primitives like LSB (Least Significant Bit) method, chaotic map, or it can use cryptographic primitives such as message authentication codes, digital signature and encryption. The watermarking techniques embed a digital watermark, which asserts the ownership of the digital media such as text, audio, image and video. The embedded watermark is extracted from the watermarked media as and when required and then is used to check its authenticity whether the media is duplicated or fabricated. The main goals of the digital watermarking are the robustness and security of the digital media (Furht, & Kirovski, 2004). A typical work flow of embedding and extraction process of digital watermark in an image is shown in Figure 1.
Figure 1. Embedding and extraction of watermark